Removal of ethanol from gasoline 8

[FredRosse]

I have seen where mixing water with E10 pump gasoline will then allow the water/ethanol mixture to separate from the gasoline. This is stated to be necessary for preservation of older (collector) vehicle fuel systems that suffer many ills from the new gasoline E10 or E15 fuels. I understand this will reduce octane rating somewhat. A few relevant questions for the fuels experts:

1. Is the water mix/separation method effective?

2. What are the disadvantages here, with respect to use in older IC engines? Understanding that labor and costs to end up with less fuel and less total heat value is an obvious result.

3. What steps may be taken to correct or adjust properties of the separated (ethanol removed) gasoline to be more compatible with old engine fuel systems?

4. Is heat distillation an option here (with proper safety precautions), and how would that be done? I remember in public high school years ago (1960s) the chemistry class ran several fractional distillations (6 teams of 5 students each) of pump gasoline in the chemistry classroom, Bunsen burners under glass containers, condensing the distillate with glass water cooled heat exchangers, all six distillations running simultaneously in a classroom with 30 students. I'll bet that is not done these days!

 

[Panther140]

I think gas boils around the same temp as ethanol. Maybe you could add water vapor after that to make the ethanol vapors seperate from the gasoline?

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[mbt22]

A gasoline/ethanol/water phase diagram (there's one in patent EP 2085460) shows how it splits. Line 1, line 2 etc. show compositions in equilibrium with each other, so decide how much water you want to add (inside the phase split area). You need to add enough water to get the ethanol down to your required spec, but not so much that you dissolve excess water in the gasoline. The points on either end of the line tell you how much water and ethanol dissolve in the gasoline phase, and how much gasoline in the ethanol/water. Mass balance to determine how much of each.

Ethanol's normal boiling point is 78 deg C. Gasoline is a complex mixture of compnents with different boiling points, so it has a vaporisatoin curve that starts about 35 deg C and finishes about 200 deg C. To complicate things, ethanol interacts with gasoline (hence the odd effects on RVP and the phase split). Yes, you can distill out ethanol by removing lighter than ethanol, then heavier than ethanol, then recombining, but the economics of doing so are not in your favour. As you note, this stuff is very dangerous and unforgiving even if you know exactly what you are doing.

Matt

 

[amorrison]

Recommend you post this question to the chemical engineering group - other topics.

 

[Lou Scannon]

I'll be impressed if you come up with a process that is cost-effective to the point of being cheaper than just finding and paying for the nearest available non-ethanal treated gasoline. I did notice that many stations in the upper midwest where I was travelling last month had special nozzles for "power equipment only", which were ethanol free (but still unleaded with decent octane).

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[140Airpower]

IMHO, hemi has the point. It is very probably cheaper to find a satisfactory gasoline free of ethanol than to remove same from ordinary gasoline AND adjust the resultant solvent mixture to a reasonable fuel.

 

[FredRosse]

140Airpower: Exactly my point no 2 of the original post, yes, I clearly already was aware of this. There are websites that advise of stations selling the non-ethanol blends. In my case the one that only cost me 2 hours labor to get some, they charge $10US per gallon. The station that charges reasonable price cost me more than 4 hours labor, and a 120 mile drive.

 

[140Airpower]

Fred, your situation leaves you with hard choices. I think removing the ethanol is the least reliable, but you could try it. Have you tried simply adding an equal quantity of water, shaking it up, letting it settle and then drawing off the gasoline from the top? The gas you get from that should be octane poor. Some ethanol will remain, but might be fairly harmless. Other gasoline additives may be reduced in concentration. The water will require disposal as a hazardous waste, etc.
Then, there is the alternative of changing the vulnerable parts of your fuel system. There must be a lot of advice on that available and maybe some kits?

 

[dgallup]

All the marinas around here sell "pure gas", don't you have any lakes closer than 2 hours drive? Nearly every gas station around here that put in tanks and pumps for E85 have changed them to "pure gas" as well, it's become very common. I hope the EPA/Fed bureaucracy see the errors of their ways sooner rather than later and get rid of the ethanol mandate.

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[mbt22]

Oh yes, I should also mention that E10 meets fuel specfications with the ethanol included. You'll lose a couple of octane numbers by removing the ethanol. The base fuel is probably a little less volatile to make up for ethanols higher vapour pressure, and of course all bets on emissions control are off.

There are probably some interesting tax implications of 'manufacturing' a new fuel, at a guess.

Matt

 

[FredRosse]

"I should also mention that E10 meets fuel specfications with the ethanol included."

What do you mean by this? What fuel specifications? The original questions are asking about fuels for engines built 50 years ago.

 

[FredRosse]

Interesting that several inputs to this thread talk about all kinds of things, but most of them do not address the original stated questions.
I tried to eliminate unwanted comments in the original post, indicating that I already knew that octane rating would go down with ethanol removal, I indicated that it was understood that labor and costs would go up, and heat value would go down. I indicated that the removal of ethanol was for old engine fuel systems.

But I get answers that often neglect the questions;
"I'll be impressed if you come up with a process that is cost-effective........
" It is very probably cheaper to find a satisfactory gasoline free of ethanol than to........"
"The gas you get from that should be octane poor"
"All the marinas around here sell "pure gas", don't you have any lakes closer than 2 hours drive?"
"Oh yes, I should also mention that E10 meets fuel specfications with the ethanol included. You'll lose a couple of octane numbers by removing the ethanol. ............ There are probably some interesting tax implications of 'manufacturing' a new fuel, at a guess."

At this point only one reply addressed the original question, to a limited extent. So many forums have persons who need to reply to questions for which they have no real answer, or comments that are not relating to the actual question. I expected more from the eng-tips forum, and still want to know if someone has real (not conjecture) answers to the original questions.

 

[140Airpower]

Fred, what are you doing about the missing lead?

 

[FredRosse]

Very funny!

 

[mbt22]

The reason you're getting the answers that you are is that what you're trying to do doesn't make sense from a process engineering point of view.

E10 at the pump must meet a specific fuel specification, as a combination of gasoline and ethanol. The gasoline is a blend of individual components so that the overall mix meets that specification (octane, anti-knock index, sulphur, aromatics, olefins, benzene, RVP, distillation curve etc). The gasoline component of E10 does not have to meet all of these, and the current allowed values are different to the 50s. See link below.

1. Is the water mix/separation method effective?
Yes, for removing ethanol. See my post above to calculate how much ethanol you have left. Repeat washings with fresh water until you reach your desired ethanol level. I can't comment on the levels of potential contaminants in your tap water, so use distilled water to be safe. There isn't a spec on dissolved water in gasoline. Consider how you're going to dispose of the contaminated water. Down the municipal sewer is almost certainly not the right option, and is probably illegal. The cost of 'real' disposal will probably make 4 hours/120 miles look attractive. This is by far the easiest an safest way of removing ethanol.

2. What are the disadvantages here, with respect to use in older IC engines? Understanding that labor and costs to end up with less fuel and less total heat value is an obvious result.
There is some helpful information regarding historic fuels differences, and specific recommendations for lead/lubricity additive for historic vehicles from the Federation of British Historic Vehicle Clubs

3. What steps may be taken to correct or adjust properties of the separated (ethanol removed) gasoline to be more compatible with old engine fuel systems?
See the link above.

4. Is heat distillation an option here (with proper safety precautions), and how would that be done?
In principle, in a batch still (as in whisky), you distill off all the material lighter then ethanol overhead in a column until the overhead material reaches your maximum allowed ethanol and put it to one side. Repeat, discarding the overhead material until the ethanol is down to an acceptable level. Blend your first overheads with the remaining material. With enough reflux, you could get a sharp enough separation to not lose enough of the middle boiling gasoline to totally mess up the blend properties. A half decent lab, backed up by using the water separation method as a quick and dirty assay, would be needed. A process design for this needs a few hours simulation/calcs, and is more than I'd do for free on a forum. Physically possible, yes. Possible in a safe and practical system, I would say no.

Matt

 

[btrueblood]

You might have better luck freeze-distilling the gasoline (after separating off any liquid water). If you can cool the mix to about -100 C, most of the hydrocarbons you want to keep will be solid, while the ethanol will remain liquid. Decant the liquid and allow to reheat. Likely some of the water left in solution will have frozen, but should separate upon remelting, since you have removed the alcohol that was holding it. Lots of maybes and assumptions in all that...but it might work, and would certainly be safer than boiling the stuff, IMO.

 

[kjoiner]

Quote from dgallup - "I hope the EPA/Fed bureaucracy see the errors of their ways sooner rather than later and get rid of the ethanol mandate."

Here is what I'm worried about:

http://www.prnewswire.com/news-releases/atlanta-area-opens-gas-first-3-e15-stations-300080180.html

I live in Atlanta and we have E10 but fortunately some stations are selling ethanol-free gas in my area. So far E10 has ruined the carburetors on my Honda mower and my Stihl trimmer. I replaced both carbs but it's not cheap. How many thousands of other power tools will require expensive service or be thrown in the trash because of E10?

Kyle

 

[140Airpower]

btrueblood, have you actually done or seen documentation of the procedure you outlined? Freezing dissolved liquid components out of a solution to get an efficient separation sounds dubious. Freezing water out of a water/antifreeze solution comes to mind.

 

[tbuelna]

All gasoline sold in the US now contains at least 10% ethanol to reduce emissions. There should be no problem using pump gas with up to 10% ethanol in any vehicle. Gasoline with more than 10% ethanol should only be used in "flex fuel" vehicles. However, the added cost of purchasing a new vehicle with a "flex fuel" engine is only around $150.

 

[GregLocock]

All gasoline sold in the US now contains at least 10% ethanol to reduce emissions buy votes in Iowa.

fixed that for you.

Cheers

Greg Locock


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